Leg extension and leg curl machines are exercise machines which are designed to isolate either the quadriceps muscles at the fronts of the operator's thighs (leg extensions), or the hamstrings muscles at the backs of the operator's thighs (leg curls), through fixing the positions of the operator's thighs and applying resistive forces to the operator's lower legs through circular paths about the operator's knee joints (the operator's muscles being developed as they oppose these resistive forces by rotating the lower legs about the knee joints in a direction opposing the resistive forces applied). In order for these exercises to be most effective at isolating the muscles involved, the positions of the thighs must remain fixed while performing the exercise.
With respect to the leg extension, it is not uncommon in a leg extension exercise movement for an operator's thighs to rotate, about the knee joints, up and off of the exercise surface. To correct this problem some equipment designers have added handles, which are secured to the machine's frame, for the operator to hold onto in order to indirectly hold his thighs down while performing the exercise movement. This solution, being indirect, puts significant stresses on the operator's forearms (which must maintain a grip), biceps (which must be contracted to hold the body down), deltoids and trapezious (which must be contracted to fix the positions of the shoulders as the biceps pull). A second approach to correcting the problem of thigh constraint during a leg extension exercise movement, taken by other equipment designers, is to apply direct thigh constraint through the use of a non-rigid thigh constraint device (such as a belt) which straps transversely across the operator's thighs from its positions of attachment on the machine's frame. This approach to thigh constraint also has disadvantages. Due to the fact that the belt is non-rigid, it applies greater stress to the outsides of the operator's thighs, where it changes direction down to its points of attachment on the machine's frame. A second disadvantage to this approach to thigh constraint is the fact that the belt is relatively difficult and time consuming to engage and disengage, especially if it is to fit snuggly against the operator's thighs.
With respect to the leg curl, it is not uncommon for an operator, upon experiencing discomfort or difficulty with the applied loads while performing leg curls, to voluntarily (or without knowing it) rotate his thighs, about the knee joints, up and off of the exercise surface. To the best of the applicant's knowledge, no type of thigh constraint device has been used specifically for the leg curl exercise. The use of handgrips (which would involve indirect thigh constraint), because of the orientation of the operator's body, would obviously be ineffective in constraining the operator's thighs in a leg curl exercise movement, and the use of a non-rigid belt-like thigh constraint device, besides suffering all of the disadvantages set forth in relation to the use of such a device on a leg extension machine, would suffer the added disadvantage of being extremely difficult and time consuming to engage or disengage from the leg curl exercise position.
In view of the advantages of fixing the positions of an operator's thighs while performing leg extensions or leg curls, and the disadvantages of fixing the positions of the thighs through an indirect method (like using handgrips), or a direct method which utilizes a non-rigid constraint device (such as a belt), the object of this invention is to introduce a simple, rigid, direct thigh constraint device which is easily adaptable to a leg extension and/or leg curl machine, and which can be quickly and easily engaged or disengaged from the operating position on such a machine, and which will not appreciably effect access to such a machine.